Fix test-network-all target in out-of-tree builds

The test-network-all target assumes the test-driver script lives in the
current working directory. This assumption breaks out-of-tree builds
because it actually lives in the source directory.

Automake 1.12 introduces `LOG_DRIVER` which defines the location of the
test driver script. Because Tor still supports Automake 1.11 we use the
default value of this variable directly. The default value uses the
configured shell for calling the test driver script and explicitly
prefixes the source directory.

Makefile.am

@@ -122,7 +122,7 @@ test-network-all: need-chutney-path test-driver $(TESTING_TOR_BINARY) src/tools/
 		echo "SKIP: $$f"; \
 	done; \
 	for f in $$flavors; do \
-		./test-driver --test-name $$f --log-file $(TEST_NETWORK_ALL_LOG_DIR)/$$f.log --trs-file $(TEST_NETWORK_ALL_LOG_DIR)/$$f.trs $(TEST_NETWORK_ALL_DRIVER_FLAGS) $(top_srcdir)/src/test/test-network.sh --flavor $$f $(TEST_NETWORK_FLAGS); \
+		$(SHELL) $(top_srcdir)/test-driver --test-name $$f --log-file $(TEST_NETWORK_ALL_LOG_DIR)/$$f.log --trs-file $(TEST_NETWORK_ALL_LOG_DIR)/$$f.trs $(TEST_NETWORK_ALL_DRIVER_FLAGS) $(top_srcdir)/src/test/test-network.sh --flavor $$f $(TEST_NETWORK_FLAGS); \
 	done; \
 	echo "Log and result files are available in $(TEST_NETWORK_ALL_LOG_DIR)."; \
 	! grep -q FAIL test_network_log/*.trs

changes/bug19421

@@ -0,0 +1,4 @@
+  o Minor bugfixes (testing):
+    - Fix the test-network-all target on out-of-tree builds by using the
+      correct path to the test driver script. Fixes bug #19421; bugfix on
+      0.2.7.3-rc.